The present invention relates to a metal heating furnace. In general, the prior art metal heating furnaces are of the direct-fired type in which burners are used to directly burn fuel. The direct-fired method may be divided into the upper roof burner system and the side burner system, both of which have the following defects:
(i) In the direct-fired method, the heat is transferred from the gaseous heat-radiating body, that is, the flames which are hot gases and are inferior in heat-transfer capability to the solid heat-radiating body. As a result, it is extremely difficult to ensure the uniformity of furnace temperature distribution required.
(ii) Recently, metal heating furnaces have become large in size. With a large metal heating furnace more than 30 meters in length and more than 10 meters in width, the flames even with higher speeds of propagation cannot reach the center portion of the furnace so that the temperature difference between the center portion and the top and side walls of the furnace reaches higher than 100.degree. C., (the center portion being lower in temperature than the top and side walls). If the quantity or rate of combustion is throttled, the energy with which the combustion mixture is blown out through the nozzle is reduced accordingly. As a result, the flame propagation is much disturbed by the turbulent flows of the products of combustion in the furnace so that the temperature difference is further enhanced and subsequently the temperature distribution is much wildly fluctuated.
(iii) Because of the disturbance of the flame propagation, the material is subject to local heating so that the qualities of the material are degraded or the fuel in more quantity than required must be burned, resulting in the losses of energy.
The present invention was made to overcome the above and other problems encountered in the prior art metal heating furnace and has for its object to provide a metal heating furnace which utilizes solid heat-radiating bodies so that the required uniformity of temperature distribution in the furnace can be maintained and energy savings can be attained and which can uniformly heat the materials so that the qualities of heated materials can be improved and at the same time the full utilization of the products of combustion can be ensured.
The present invention will become more apparent from the following description of preferred embodiments thereof taken in conjunction with the accompanying drawings.